Toner for developing an electrostatic latent image can be prepared using a grinding method (sometimes also referred to as a pulverizing method) or a polymerizing method. In the grinding method, a synthesized resin, a colorant, and optionally other additives are dissolved and mixed together. The resulting mixture is ground into particles, which are classified in order to obtain particles having a desired diameter. In the polymerizing method, a polymerizable monomer, a pigment, a polymerization initiator and optionally other additives such as, for example, a crosslinking agent or an antistatic agent, are homogeneously dissolved or dispersed to form a polymerizable monomer composition. The polymerizable monomer composition may be dispersed with an agitator in an aqueous dispersion medium containing a dispersion stabilizer so as to form droplet particles of the polymerizable monomer composition. The temperature may be increased and a suspension-polymerization process may be performed to obtain color polymerization particles having the desired particle diameters, that is, the polymerization toner.
Characteristics of toner required for electrophotography and electrostatic recording techniques include a small particle diameter and a narrow particle diameter distribution. These properties lead to high image quality and high resolution, low-temperature fixing, high glossiness, and/or longer preservation or storability characteristics. Low-temperature fixing, high glossiness and preservation characteristics may also be obtained by controlling the structure of the toner.
Images formed using an imaging apparatus such as an electrophotographic copier, require a high degree of precision. Conventionally, toner obtained using a grinding method is commonly used in imaging apparatuses. However, when the grinding method is used, colorant particles formed are likely to have a wide particle diameter distribution. Thus, to obtain desirable toner characteristics, the colorant particles need to be classified in order to obtain a narrow particle diameter distribution. With respect to conventional grinding methods, the degree to which toner particle diameter and toner structure can be controlled is limited, and thus the likelihood of a new design having a significant change in the major characteristics of the toner is relatively low.
Recently, polymerization toners of which particle sizes can be easily controlled and prepared without complicated manufacturing processes such as a classifying process have received significant attention. When toner is prepared by polymerization, polymerization toner having a desired particle diameter and distribution can be obtained without a grinding or classifying process. For example, toner can be manufactured using a metal salt such as MgCh or NaCl as an agglomerating agent.
To obtain high printing performance and high image quality, in addition to particle diameter and particle diameter distribution control, other functional properties such as fixing and durability characteristics of toner also need to be considered.